A number of instruments exist for mapping optical elements, and especially for ophthalmic use. Such instruments generally use a Hartman Shack matrix for analyzing the refractions of a beam of light transmitted through the spectacle lens. In U.S. Pat. No. 5,825,476, there is described such a system, and other such systems are cited in that patent. One of the major disadvantages of many of such prior art instruments is that the user places the spectacle frames directly on the measurement table, such that the reference plane used to align the lenses is then effectively that of the frame itself, and not of the lenses being mapped. Consequently, if the lens form has a large element of sag, or if the lens has a large tilt, then the mapping results obtained may be inaccurate. Furthermore, in many such prior art instruments, the frames have to be aligned manually or by means of motors in order to align the mechanical center of the lenses being measured with the measurement beam.
There therefore exists a need for a spectacle measurement system, which can map both lenses automatically and which overcomes at least some of the disadvantages of prior art systems and methods.
The disclosures of each of the publications mentioned in this section and in other sections of the specification, are hereby incorporated by reference, each in its entirety.